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Unnecessary flu epidemics – what is preventing vaccination?

In the last of our series on economics and disease control, Lucia Algara Bradshaw discusses vaccine uptake for influenza and differing immunisation policies around the world.

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Influenza is an infectious disease which affects millions of people year on year, and leads to detrimental social, economic and productive losses. With 4 to 50 million symptomatic cases in the EU/EEA each year, and 15,000 to 70,000 European deaths each year, this disease has huge repercussions despite vaccines being widely available.

The World Health Organisation (WHO) recommends seasonal influenza vaccination to those who have a higher risk of developing complications following infection - including pregnant women, children aged 6 - 59 months, the elderly and those with chronic medical conditions – and to health-care workers. Yet, there is still a large variability found when examining and comparing different countries’ national immunisation policies.

There are considerable disparities in the immunisation policies in operation across the world; the US, for instance, recommends that everyone aged 6 months or older should get a seasonal influenza vaccine, whereas some countries do not even have an immunisation program. Within the 59% of WHO Member States that do, there are stark differences in what groups of people should be vaccinated. The underlying reasons for this were explored in a review by Principi et al. (2018) and the main reason reported was the lack of quantifiable information on the social, economic and clinical repercussions influenza has. Due to the misdiagnosis of influenza, because of many pathogens that cause very similar symptoms (denoted influenza-like illnesses, ILIs), the economic impact of influenza is hard to determine. On top of this, calculating the cost-effectiveness of different influenza vaccines on various groups of people is difficult, especially due to their indirect advantages, like herd immunity, which must be considered.

Despite differences between the age at which citizens were regarded to be elderly, which ranged from 54 to 64, all EU/EEA Member States recommended vaccination of older age groups in the 2017-2018 season. However, none of the countries met the targeted coverage of 75%; this is extremely alarming, due to the fact that 90% of influenza-associated deaths occur in people aged 65 or older. Furthermore, according to the European Centre for Disease Prevention and Control (ECDC), the influenza vaccination uptake amongst high risk groups has declined over the past seven years. Not only is this worrying in terms of protecting people against annual influenza, it is also particularly concerning in terms of preparing for the next influenza pandemic.

No particular reason lies behind this low and declining uptake of vaccines - instead, reduced confidence in vaccine effectiveness and safety, lack of recommendations by health professionals and a decline in citizen’s trust following the 2009 pandemic could all be responsible. What can be said with more certainty is that in European countries with lower resources, the low uptake is mainly due to the more limited vaccine availability - in these areas influenza is not classified as a high priority disease. Again, the lack of precise estimates of the social and economic burden of influenza could underlie this.

Overall, despite the significant differences in national immunisation policies, the prominent issue in need of attention is the declining vaccination uptake.


References:

Principi, Nicola et al. “Influenza immunization policies: Which could be the main reasons for differences among countries?.” Human vaccines & immunotherapeutics vol. 14,3 (2018): 684-692. doi:10.1080/21645515.2017.1405188

Jorgensen, Mereckiene, et al. “How close are countries of the WHO European Region to achieving the goal of vaccinating 75% of key risk groups against influenza? Results from national surveys on seasonal influenza vaccination programmes, 2008/2009 to 2014/2015.” Vaccine, vol 36, 4, (2018): 442-452, https://doi.org/10.1016/j.vaccine.2017.12.019.

EDRC and WHO. “Low uptake of seasonal influenza vaccination in Europe may jeopardise capacity to protect people in the next pandemic.” Press release (2018). PDF: https://www.ecdc.europa.eu/sites/default/files/documents/ECDC-WHO_PR_InfluenzaOverviewVaccine.pdf


Lucia Algara Bradshaw is a third year student in Natural Sciences at Homerton College, Cambridge. She has a strong interest in Public Health, especially in the control of infectious diseases. Over the summer 2019, she worked for Dr Flavio Toxvaerd on a project on the economics of seasonal flu and herd immunity.